Reconfigurable Electronics Research Articles

Electrically tuneable terahertz metasurface enabled by a graphene/gold bilayer structure

Reconfigurable terahertz electronics devices with high tuneability are pivotal for next-generation high speed wireless communication and sensing technologies. Significant challenges exist for realizing these devices, particularly on the design of smart metastructures that can manipulate electromagnetic radiation at the terahertz frequencies and the fabrication of devices with effective tuneability and reconfigurability. Here, we incorporate graphene into a graphene/gold bilayer superimposed metamaterial structure, which enables efficient electrical tuning of terahertz waves. A 0.2 THz frequency-selective absorber is designed and experimentally developed using this graphene/gold bilayer metamaterial approach. The device demonstrates 16 dB amplitude tuning at 0.2 THz resonance and over 95% broadband modulation at just 6 V bias voltage while maintaining a benchmark high-quality factor resonance performance. The design and fabrication methods presented can be readily applied to produce a myriad of tuneable terahertz devices required for high-speed, reconfigurable THz wireless communication and sensing technologies.

Highly Efficient Polarization‐Controlled Electrical Conductance Modulation in a van der Waals Ferroelectric/Semiconductor Heterostructure

AbstractUtilizing the unique in‐plane/out‐of‐plane polarization coupling in ferroelectric van der Waals α‐In2Se3, ferroelectric‐polarization‐controlled electrical conductance modulation in two‐dimensional (2D) MoS2 with a large dynamic range of over 5 orders of magnitude and excellent non‐volatility is demonstrated. This highly efficient control of the electrical conductance is facilitated by enhanced capacitive coupling through atomic‐layer‐deposition‐grown Al2O3 as the dielectric medium. By varying the in‐plane poling bias to the ferroelectric α‐In2Se3, the electrical conductance of vertically stacked 2D MoS2 can be tuned continuously. This approach enables simplified device design and provides great flexibility in device integrations, and it can be applied in principle to manipulate the electronic states in any 2D semiconductors for various applications such as transistors, tunneling devices, and reconfigurable electronics. The results also provide insight into the ferroelectric polarization screening by ambient chemical species, highlighting the need for surface passivation, and/or device encapsulations.

Ion-cluster-mediated ultrafast self-healable ionoconductors for reconfigurable electronics

Implementing self-healing capabilities in a deformable platform is one of the critical challenges for achieving future wearable electronics with high durability and reliability. Conventional systems are mostly based on polymeric materials, so their self-healing usually proceeds at elevated temperatures to promote chain flexibility and reduce healing time. Here, we propose an ion-cluster-driven self-healable ionoconductor composed of rationally designed copolymers and ionic liquids. After complete cleavage, the ionoconductor can be repaired with high efficiency (∼90.3%) within 1 min even at 25 °C, which is mainly attributed to the dynamic formation of ion clusters between the charged moieties in copolymers and ionic liquids. By taking advantages of the superior self-healing performance, stretchability (∼1130%), non-volatility (over 6 months), and ability to be easily shaped as desired through cutting and re-assembly protocol, reconfigurable, deformable light-emitting electroluminescent displays are successfully demonstrated as promising electronic platforms for future applications.

Selectively biased tri-terminal vertically-integrated memristor configuration

Memristors, when utilized as electronic components in circuits, can offer opportunities for the implementation of novel reconfigurable electronics. While they have been used in large arrays, studies in ensembles of devices are comparatively limited. Here we propose a vertically stacked memristor configuration with a shared middle electrode. We study the compound resistive states presented by the combined in-series devices and we alter them either by controlling each device separately, or by altering the full configuration, which depends on selective usage of the middle floating electrode. The shared middle electrode enables a rare look into the combined system, which is not normally available in vertically stacked devices. In the course of this study, it was found that separate switching of individual devices carries over its effects to the Complete device (albeit non-linearly), enabling increased resistive state range, which leads to a larger number of distinguishable states (above SNR variance limits) and hence enhanced device memory. Additionally, by applying a switching stimulus to the external electrodes it is possible to switch both devices simultaneously, making the entire configuration a voltage divider with individual memristive components. Through usage of this type of configuration and by taking advantage of the voltage division, it is possible to surge-protect fragile devices, while it was also found that simultaneous reset of stacked devices is possible, significantly reducing the required reset time in larger arrays.

Dual‐Mode Organic Electrochemical Transistors Based on Self‐Doped Conjugated Polyelectrolytes for Reconfigurable Electronics (Adv. Mater. 23/2022)

Organic Electrochemical Transistors A dual ionic transport property of self-doped conjugated polyelectrolytes is reported by Thuc-Quyen Nguyen and co-workers in article number 2200274: they can be both doped and dedoped upon the interaction with anions (blue) and cations (red) in an electrolyte, respectively. This discovery enables dual-mode organic electrochemical transistors, paving the way for the use of organic devices in emerging reconfigurable electronics.

Self-Healable and Recyclable Dual-Shape Memory Liquid Metal-Elastomer Composites.

Liquid metal (LM)–polymer composites that combine the thermal and electrical conductivity of LMs with the shape-morphing capability of polymers are attracting a great deal of attention in the fields of reconfigurable electronics and soft robotics. However, investigation of the synergetic effect between the shape-changing properties of LMs and polymer matrices is lacking. Herein, a self-healable and recyclable dual-shape memory composite, comprising an LM (gallium) and a Diels–Alder (DA) crosslinked crystalline polyurethane (PU) elastomer, is reported. The composite exhibits a bilayer structure and achieves excellent shape programming abilities, due to the phase transitions of the LM and the crystalline PU elastomers. To demonstrate these shape-morphing abilities, a heat-triggered soft gripper, which can grasp and release objects according to the environmental temperature, is designed and built. Similarly, combining the electrical conductivity and the dual-shape memory effect of the composite, a light-controlled reconfigurable switch for a circuit is produced. In addition, due to the reversible nature of DA bonds, the composite is self-healable and recyclable. Both the LM and PU elastomer are recyclable, demonstrating the extremely high recycling efficiency (up to 96.7%) of the LM, as well as similar mechanical properties between the reprocessed elastomers and the pristine ones.

Monolithic and Single-Crystalline Aluminum-Silicon Heterostructures.

Overcoming the difficulty in the precise definition of the metal phase of metal–Si heterostructures is among the key prerequisites to enable reproducible next-generation nanoelectronic, optoelectronic, and quantum devices. Here, we report on the formation of monolithic Al–Si heterostructures obtained from both bottom-up and top-down fabricated Si nanostructures and Al contacts. This is enabled by a thermally induced Al–Si exchange reaction, which forms abrupt and void-free metal–semiconductor interfaces in contrast to their bulk counterparts. The selective and controllable transformation of Si NWs into Al provides a nanodevice fabrication platform with high-quality monolithic and single-crystalline Al contacts, revealing resistivities as low as ρ = (6.31 ± 1.17) × 10–8 Ω m and breakdown current densities of Jmax = (1 ± 0.13) × 1012 Ω m–2. Combining transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the composition as well as the crystalline nature of the presented Al–Si–Al heterostructures, with no intermetallic phases formed during the exchange process in contrast to state-of-the-art metal silicides. The thereof formed single-element Al contacts explain the robustness and reproducibility of the junctions. Detailed and systematic electrical characterizations carried out on back- and top-gated heterostructure devices revealed symmetric effective Schottky barriers for electrons and holes. Most importantly, fulfilling compatibility with modern complementary metal–oxide semiconductor fabrication, the proposed thermally induced Al–Si exchange reaction may give rise to the development of next-generation reconfigurable electronics relying on reproducible nanojunctions.

Dual-Mode Organic Electrochemical Transistors Based on Self-Doped Conjugated Polyelectrolytes for Reconfigurable Electronics.

Reconfigurable organic logic devices are promising candidates for next generations of efficient computing systems and adaptive electronics. Ideally, such devices would be of simple structure and design, be power efficient, and compatible with high-throughput microfabrication techniques. This work reports an organic reconfigurable logic gate based on novel dual-mode organic electrochemical transistors (OECTs), which employ a self-doped conjugated polyelectrolyte as the active material, which then allows the transistors to operate in both depletion mode and enhancement mode. Furthermore, mode switching is accomplished by simply altering the polarity of the applied gate and drain voltages, which can be done on the fly. In contrast, achieving similar mode-switching functionality with other organic transistors typically requires complex molecular design or multi-device engineering. It in shown that dual-mode functionality is enabled by the concurrent existence of anion doping and cation dedoping of the films. A device physics model that accurately describes the behavior of these transistors is developed. Finally, the utility of these dual-mode transistors for implementing reconfigurable logic by fabricating a logic gate that may be switched between logic gates AND to NOR, and OR to NAND on the fly is demonstrated.

Strain-dependent phase-change devices based on vanadium dioxide thin films on flexible glass substrates

Smart materials offering tunable electrical properties in response to external stimuli are in high demand for their usage in reconfigurable electronics. This study reports the stability and reversibility of insulator-to-metal transition (IMT) in a vanadium dioxide (VO2) thin film grown on flexible glass substrates under the external strain. The systematic application of the external strain was used to demonstrate red and blue shifts in the Raman spectra (ωV-O) and the corresponding change in the IMT critical temperature. The effects of externally applied tensile strain on the electrical resistance of the VO2 thin film were discussed concerning the stability and repeatability of the IMT. We demonstrated that the electrical performance of the thin film was nondegradable, although the sample was subjected to multiple cycles of tensile strain. Moreover, these results not only provide essential knowledge for understanding the correlation between the external strain and physical properties of VO2 thin films but also suggest their applicability as strain-dependent phase-change devices.

Two-dimensional reconfigurable electronics enabled by asymmetric floating gate

Two-dimensional reconfigurable electronics enabled by asymmetric floating gate

Reconfigurable InSe Electronics with van der Waals Integration

AbstractAs a 2D semiconductor, indium selenide (InSe) has shown great potentials in electronic and optoelectronic applications attributed to high carrier mobility and moderately large bandgap. However, switchable doping polarity of intrinsic InSe by electrical gating is not yet demonstrated, which is essential for applications in complementary electronics. In this work, the ambipolarity of InSe is realized and exploited through the van der Waals (vdW) integration with metal electrodes, which gets rid of the Fermi‐level pinning at the metal/semiconductor interfaces. On this basis, InSe field‐effect transistors (FETs) with controllable polarities are reconfigured with a dual‐gate structure, functioning as both unipolar FETs and p–n diodes. The p‐ and n‐type operations of the unipolar FETs are dynamically switched with on–off ratios of 106 and 109, respectively. Meanwhile, p–n diodes with a rectification ratio of 106 and high photodetection performance are also demonstrated. This work paves a promising way for InSe‐based reconfigurable complementary electronics and optoelectronics.

Ultrafast self-healing and self-adhesive polysiloxane towards reconfigurable on-skin electronics

We develop a novel polysiloxane elastomer with ultrafast self-healing capability, robust mechanical properties, universal self-adhesiveness, and reconfigurability towards any shapes, which is potential for on-skin electrophysiological electrodes.

Determination of Silicon Electrical Properties Using First Principles Approach

Silicon nanowires have attracted attention as basis for reconfigurable electronics. However, as the size decreases, the electronic properties of the nanowires vary as a result of confinement, strain and crystal topology effects. Thus, at the thin diameter regime the band gap of Silicon nanowires can no longer be derived from a simple extrapolation of the isotropic bulk behaviour. This study compares band gap parameters in sub 10nm nanowires obtained from first-principles density-functional band structure calculations with extrapolations using continuum theory in order to rationalize the changes of the overall conductance, resistance and band gap. The device consists of silicon nanowire of size between 1 nm to 6nm. The results indicate an increase of, both the energy gap and the resistance along with reduced conductivity for the thinnest wires and a dependence on the crystal orientation with gaps reaching up to 4.3 eV along <111>, 4.0 eV along <110>, and 3.7 along <100>.

Spatially selective adhesion enabled transfer printing of liquid metal for 3D electronic circuits

3D printing, well known by the public, is regarded as an important symbol of entering the next industrial revolution that is well suited for the development of 3D electronics. However, reducing the manufacturing cost and time of 3D electronics is still one of the biggest challenges for its wide application. With low melting point, high conductivity, and reversible stiffness, gallium-based liquid metals are of great importance in developing multifunctional 3D electronic circuits. While, most research only use liquid metal as filler in 3D channels, which greatly weakened the interface function of liquid metal. Here, we report a straightforward, practical, and rapid fabrication strategy for multifunctional 3D electronic circuits based on 3D printing and a spatially selective adhesion mechanism of liquid metal inks. This method is applicable to diverse 3D structures with various mechanical properties and material types. A series of electronic circuits were printed out, and conceptual experiments were performed to demonstrate and justify the working of the new approach. Because of the phase transition and contact welding, the liquid metal based 3D electronic circuits show excellent stiffness variation and assemblability, which are promising to fabricate complex flexible 3D electronic systems, reconfigurable 4D electronics, and variable stiffness robots.

A Locally Actuatable Soft Robotic Film for Actively Reconfiguring Shapes of Flexible Electronics.

Actively reconfigurable flexible electronics enabled by robotic technologies would provide opportunities to extensively broaden the application areas of flexible electronics compared with their passively flexible counterparts. Diverse reconfigurable shapes can be enabled by localized control of the film-type electronics while keeping a thin form factor for flexible electronics. The flexible electronics are usually designed to be thin to lower mechanical stress or strain when bending. In this article, we present a locally actuatable film designed to control actuating regions, bending directions, and curvatures by the electrical inputs. The film is in a thin form factor with multichannels realized by the proposed method of crimping electrical wires over shape memory alloy wires. The industry standard process should be convenient in terms of scaling up, increasing channels, or adding reconfigurable shapes for new applications. We demonstrate shape-changeable displays, self-rollable photovoltaics, and light art to prove the feasibility of the concept.

Soft, Bistable Actuators for Reconfigurable 3D Electronics.

Existing strategies for reconfigurable three-dimensional (3D) electronics are greatly constrained by either the complicated driven mechanisms or harsh demands for conductive materials. Developing a simple and robust strategy for 3D electronics reconstruction and function extension remains a challenge. Here, we propose a solvent-driven bistable actuator, which acts as a substrate to reconstruct the combined 3D electronic device. Extraction of silicon oil from a hybrid poly(dimethylsiloxane) (PDMS) circle sheet buckles the dish to a bistable structure. The ultraviolet (UV)/ozone treatment on one surface of the PDMS structure introduces an oxidized layer, yielding a bilayered, solvent-driven bistable smart actuator. The snap-back stimulus to the oxidized layer differs from the snap-through stimulus. Experimental and numerical studies reveal the fundamental regulations for buckling configurations and the bistable behavior of the actuator. The prepared bistable actuator drives the bonded kirigami polyimide (PI) sheets to diverse 3D structures from the original bending configuration, reversibly. A frequency-reconfigurable electrically small monopole antenna is presented as a demonstration, which paves a way for the applications of this actuator in the field of reconfigurable 3D electronics.

Gaussian Process Regression Based Robust Optimization with Observer Uncertainty for Reconfigurable Self-x Sensory Electronics for Industry 4.0

Abstract This paper presents a robust optimization technique for the reconfigurable measurement of sensory electronics for industry 4.0 to obtain a robust solution even in the presence of observer uncertainty using a cost-effective performance measurement method. The extrinsic evaluation of the proposed methodology is performed on an indirect current-feedback instrumentation amplifier (CFIA), which is a fundamental part of sensory systems. To reduce the CFIA device performance evaluation set-up cost, a low-cost test stimulus is applied to the circuit under test, and the output response of the circuit is examined to correlate with the device’s performance parameters. Due to the complexity of the smart sensory electronics search space, the meta-heuristic optimization algorithm is being selected as an optimizer. For objective space or observer uncertainty, the Gaussian process regression from the Bayesian statistical regression process is used to estimate the uncertainty level efficiently. Six different classical metrics have been used to evaluate the regression model accuracy. The highest achieved average expected error metrics value is 0.313, and the minimum value of correlation performance metrics is 0.908. The device is implemented using 0.35 μm austriamicrosystems technology.

Self-healing liquid metal composite for reconfigurable and recyclable soft electronics

Soft electronics and robotics are in increasing demand for diverse applications. However, soft devices typically lack rigid enclosures which can increase their susceptibility to damage and lead to failure and premature disposal. This creates a need for soft and stretchable functional materials with resilient and regenerative properties. Here we show a liquid metal-elastomer-plasticizer composite for soft electronics with robust circuitry that is self-healing, reconfigurable, and ultimately recyclable. This is achieved through an embossing technique for on-demand formation of conductive liquid metal networks which can be reprocessed to rewire or completely recycle the soft electronic composite. These skin-like electronics stretch to 1200% strain with minimal change in electrical resistance, sustain numerous damage events under load without losing electrical conductivity, and are recycled to generate new devices at the end of life. These soft composites with adaptive liquid metal microstructures can find broad use for soft electronics and robotics with improved lifetime and recyclability.

(Invited) Smart Nanomembranes for Multifunctional Sensors and Reconfigurable Electronics

Following the path of More than Moore requirements, functionalization and diversification of integrated circuits becomes an urgent topic. Integration of functions in a single chip is also an important issue in wearable and portable electronics. Smart nanomembranes, with thickness ranging from several to hundreds of nanometers, is considered as an ideal candidate in these circumstances for its flexibility. The word “smart” shows that these nanomembranes can perform sensing and actuating tasks by themselves, which largely reduces the complexity of flexible sensors and devices. The talk given here is focused on our recent progress in the development of smart nanomembranes for flexible sensors and reconfigurable electronics. Combined with sensing-type smart nanomembranes as palladium and hydrogel, we designed a multifunctional soft platform to detect different kinds of signals (e.g. gas and humidity), which can be integrated into a smart digital dust device. Furthermore, smart nanomembranes with actuation properties were applied in reconfigurable electronic devices. These nanomembrane-based devices are able to be stabilized in different configurations to provide particular and switchable electronic functions. These investigations highlight the great potential of smart nanomembranes in flexible electronics. And their unique sensing and actuating properties paves the way to intelligent robots in micro and nanoscale.

Reconfigurable electronics by disassembling and reassembling van der Waals heterostructures

Van der Waals heterostructures (vdWHs) have attracted tremendous interest owing to the ability to assemble diverse building blocks without the constraints of lattice matching and processing compatibility. However, once assembled, the fabricated vdWHs can hardly be separated into individual building blocks for further manipulation, mainly due to technical difficulties in the disassembling process. Here, we show a method to disassemble the as-fabricated vdWHs into individual building blocks, which can be further reassembled into new vdWHs with different device functionalities. With this technique, we demonstrate reconfigurable transistors from n-type to p-type and back-gate to dual-gate structures through re-stacking. Furthermore, reconfigurable device behaviors from floating gate memory to Schottky diode and reconfigurable anisotropic Raman behaviors have been obtained through layer re-sequencing and re-twisting, respectively. Our results could lead to a reverse engineering concept of disassembled vdWHs electronics in parallel with state-of-the-art vdWHs electronics, offering a general method for multi-functional pluggable electronics and optoelectronics with limited material building blocks.